Fetal Pig Dissection Home Page


    Now that you have learned about your subject you can begin to investigate the inner workings of a pig.  You will begin with some observations and then you will begin the dissection of the fetal pig.  You should start at the top with the external anatomy.  You can then move through the dissection by scrolling down.  


    Part I

    External Anatomy

    Oral Cavity


    Thoracic and Abdominal Cavities


               Thoracic cavity 

               Abdominal cavity


    Part II

    Cardiovascular System

      Major Blood Vessels


    Urogenital System

          Urinary System

           Male Reproductive System

           Female Reproductive System


    Part III

    (No Dissection Necessary)


    Skeletal System

     Muscular System


    Fetal Pig Organ Review - Labeled pictures of all the organs you need to know.




    Part I - Dissection of the Fetal Pig


    First obtain your fetal pig.  Lay your pig in your dissection pan and examine the external features of your pig.


    You should notice that your pig has a cut on the right side of its neck. This is where the blood was drained from the pig and latex was injected into the arteries and veins of the pig.


    Which color represents the veins?  _________  Why?



    Which color represents the arteries? __________ Why?






                                ventral - towards the belly
    Dorsal - towards the back

    Anterior - to the front

    Posterior - to the back



    External Anatomy of the Fetal Pig



    Click here for a labeled diagram of the external features of the fetal pig.


    Look at your pig.


    Observe the:


    v     Large head

    v     Short Neck

    v     Trunk with two pairs of appendages.


    What have the nails of the pig been modified to be?




    v     Tail -which is an extension of the vertebral column

    v     Umbilical cord




    What is the function of the Umbilical cord?




    v     Nipples (external openings of the mammary glands; found on both male and female pigs)

    v    Hair


    Where do you find hair on your pig?





    v     Anus (located under the tail)


    The anus is the opening for what body system?





    Where is the other opening for this system?




    v     Urogenital opening


    Females -anterior to the anus;  a small fleshy urogenital papilla projects from the urogenital opening


    Males -posterior to the umbilical cord.


    In males what to systems are joined in the urethra?




    What sex is your pig? (You are responsible for identifying both!) 

    Observation of the Oral Cavity of the Fetal Pig


    What structures should you find in the oral cavity?





    Insert a pair of scissors into the pig's mouth and cut posteriorly for 4 cm. Repeat on the other side of the mouth. Place your thumb on the tongue at the front of the mouth and gently push down to open the mouth.  You will tear some of the tissues.  This is ok.


     Oral Cavity Opened





    Observe thefollowing structures.


    v     Teeth - undeveloped on both jaws


    WWhat are the functions of the teeth?




    v     Tongue - partly attached to the lower jaw; extends posteriorly and is attached to the bony structure at the back of the oral cavity


    What are the functions of the tongue?









    v     Hard palate - ridges of the roof of the mouth, separates the oral cavity from the nasal passages

    v     Soft Palate - smooth region posteriorto the hard palate.


    In humans what structure hangs from the soft palate?





    Observation of the Pharynx of the Fetal Pig




    The Pharynx is dorsal to the oral cavity and has three openings:  the glottis, the esophagus and the trachea.



    The pharynx is a passageway for what two substances?






    Push down on the tongue to open the jaws.  You will see a flap pointed dorsally;  this is theepiglottis.  The epiglottis is the flapthat covers the glottis.  The glottis is the opening between the oral cavity and the trachea. 



    What is the function of the trachea?




    What is the function of the epiglottis?





    The opening to the esophagus is located posterior and dorsal to the glottis. 



    What is the function of the esophagus?







    Note that theglottis is located very close to the esophagus.



    Explain the relationship between the esophagus, the epiglottis and the glottis.





    Insert a blunt probe into the glottis.  Note that it enters the trachea.  Now insert the probe into the esophagus.  Notice that the esophagus is underneath the trachea.



    The nasopharngeal opening is posterior to the soft palate. The nasopharyngeal opening leads from the oral cavity to the nasal passages.



    Observation of the Thoracic Cavity and Abdominal Cavities




    Place the fetal pig on its back in the dissecting pan. Tie a cord around one forelimb, bring the cord under the pan, and tie the cord to the other forelimb. Repeat with the hind limbs. 


     Following the numbered incisions use scissors to expose the thoracic and abdominal cavities. 



    The diaphragm is the structure that separates the thoracic cavity from the abdominal cavity.



    Cut from the diaphragm up to the hairs in the throat region, then make the lateral cuts. Pull back the flaps formed by these cuts to reveal the thoracic cavity. 



    What organs arelocated in the thoracic cavity?






    Cut posteriorly from the diaphragm to theumbilical cord.  Make a flap by cuttingaround the umbilical cord.  Make lateral cuts and pull back the flaps to expose the abdominal cavity.


    What two cavities does the diaphragm separate?






    What organs are located in the abdominal cavity?






     What are the major organ systems that are located in the Thoracic cavity?(2)






     What are the major organ systems located in the abdominal cavity? (2)



    Observation of the Neck Region of the Fetal Pig


    Locate and observe the thymus gland, larynx, trachea, esophagus and thyroid gland.

    Move the skin a part in the neck region to expose the neck region.  You may have to make lateral incisions to pullthe skin back.  Cut through the muscle to expose the thymus gland. The thymus gland is part of the immune system.  Certain white blood cells (T Lymphocytes) mature in the thymus.


     Neck Region

    Probe into the deeper layers of the neck.  Toward the center, under several layers of muscle, you will find the larynx and the trachea.  The larynx is also called the voicebox. The larynx sits over the trachea, also called the windpipe.  The esophagus is located dorsally to the trachea.  The esophagus connects the oral cavity to the stomach.

    The thyroid gland islocated posterior to the larynx and on top of (ventral to) the trachea. The thyroid gland secretes hormones, including thyroxine.



      What does the hormone thyroxine control?


      What are hormones?





    Observation of the Thoracic Cavity of the Fetal Pig



    The diaphragm of mammals divides the body into two cavities, the thoracic cavity and theabdominal cavity.  The thoracic cavity contains the heart and lungs.


    Fold back the chestwall flaps.  You will observe a thin membrane that divides the thoracic cavity into three parts:  two pleural cavities and one pericardial cavity.  Each lung is found in a separate pleural cavity;  the lungsare respiratory organs used for gas exchange.  The heart is located in the pericardial cavity:  it functions as a pump in the circulatory system. Tear the membranes to reveal the heart and lungs.

    Examine the lungs.  Notice the left lung (on the pig's left side) has three lobes while the right lung has four lobes.


      What is the path of air from the nasal passage to the lungs?  (What organs does it go through?)





    Observation of the Abdominal Cavity of the Fetal Pig



    The abdominal cavity and organs are also lined with a membrane.  The mesenteric membranes support the organs of the abdominal cavity.  If your pig is filled withdark brown fluid (clotted blood) rinse it out in the sink.  



    Abdominal Cavity
    Abdominal Cavity2


    The liver is the largest organ in the abdomen.  It is dark drown in color and fits snuggly into the diaphragm.  The liver performs the following vital functions.



    1.       produces _____________

    2.       stores glycogen

    3.       destroys red blood cells

    4.       maintains blood glucose levels

    5.       produces blood proteins



    The stomach, small intestines and large intestines are all parts of the ______________ system.

    Locate the stomach;  it is a large sac located dorsal to the liver on the leftside of the pig.  The stomach stores food;  it contains several gastric glands that secrete gastric juice, used in the digestion of food. The esophagus carries food from the mouth to the stomach.  Find where the esophagus enters the stomach.



      What"pipe" leads to the stomach?



      What allows the food to go into the esophagus and not the trachea?



      What is the pH of the stomach?  How does it get that way?



      What organic molecule is digested in the stomach?  What enzyme is responsible?



    Locate the small intestinewhere it exits the stomach.  It is a mass of loops and folds that is held together by mesentery.  The small intestine receives secretions from the pancreas and gall bladder. 



    What is the major function of the small intestines?



      What membrane holds the small intestines in place?



      What are the monomers that make up proteins, carbohydrates and fats?



      A pig can eat all of the major organic molecules that you can in his pig slop.  Give an example of a protein, carbohydrate and a fat that the pig could get in his slop.



    Locate the gallbladder.  It is embedded in the liver on the underside of the right lobe.  It is a small greenish sac.


      What does the gallbladder store?


      What does bile do?  Where does it do its job?


    Locate the pancreas under the stomach.  It is a diffuse gland found in the mesentery  between the stomach and the small intestine.  The pancreas is both anexocrine gland and an endocrine gland.  The pancreas producesand secretes pancreatic juices that aid in the digestion of food. 


      What does the pancreas produce?



      What are the four enzymes that the pancreas produces and what does each break down?




    As an endocrine gland,the pancreas secretes the hormones insulin and glucagon.  These hormones are secreted into the blood stream.


    Locate the spleen. It is a long, flat reddish organ attached to the stomach by mesentery.  The spleen is a lymphoid organ in the immune system.  It stores both red and white blood cells.

    Open one side of the stomach and note the appearance of the interior surface. 

    Is it smooth or rough?



      Why does the pig have such a long intestine?



      Slit open the intestine.  Is the lining of the intestine smooth or rough?


    Look at the inside of the intestine using a dissecting scope.  What do you see?


      What are the structures you saw above called?


      What is the function of the villi? 




    The Cardiovascular System of the Fetal Pig



    The heart pumps blood, circulating it to all parts of the body. 

     Thoracic Cavity




      What blood vessel carries blood away from the heart?


      What blood vessel carries blood to the heart?



      What structure joins the arterioles to the venules?



    Blood is pumped from the heart under pressure.  Arteries have thick walls that expand when thepressurized blood enters them.  Blood moves away from the heart through the larger arteries and the smaller arterioles.  Veins have thinner wallsand valves that prevent blood from flowing backwards in the veins.  Blood returns to the heart from the tissues via the larger veins and smaller venules.  Blood is pumped away from the heart by the contraction of thebeating heart.  Blood is returned to the heart when skeletal musclescontract and press against the veins and venules; this forces blood to move through the veins back toward the heart.  Capillaries have exceptionally thin walls; this allows the exchange of materials from the blood with the tissue fluid, which surrounds the capillaries.

    Circulation is different in adults and in fetuses.  In the adult, blood is oxygenated in the lungs and nutrient molecules enter the blood in the digestive tract. In the fetus, the lungs and digestive system do not function.  Fetal blood obtains oxygen and nutrients when diffusion exchange occurs with the mother's blood in the placenta.



    Where does the systemic circuit move blood?



      Where doesthe pulmonary circuit move blood?



      What is the main artery that leaves the heart?



      What is the main vein that returns blood to the heart?



      How many chambers are found in the mammalian heart?


      What is the function of the ventricles?



      What is the function of the atria?


    Where does the right side of the heart pump blood? 



      Where does the left side of the heart pump blood?



      Trace the path of blood as it moves from the right ventricle to the lungs.




      Trace thepath of blood as it moves from the left ventricle to the kidneys.





    Observation of the Blood Vessels of the Fetal Pig



    In the fetal pig the pulmonary arteries and veins are not functional. 

    In your pig thearteries have been injected with red latex and the veins have been injected with blue latex.  Refer to Fetal Pig Heart as you observe the following structures.



    Pulmonary Circuit



      What isthe function of the pulmonary circuit?






      Locate the pulmonary trunk.


       What color is it in your pig?  Explain.







      Observe the pulmonary trunk and notice that it seems to connect directly with the aorta.  This connection is the arterial duct.  In the fetus, blood passes through to the aorta without going to the lungs.  This duct is closed in adults.


      Locate thepulmonary arteries that leave the pulmonary trunk and go to the lungs. 


      What color are they?  Explain.







      Locate the pulmonary veins as they leave the lungs; trace them back to the heart.   


      What color are they?  Explain.






    Systemic Circuit


    The systemic circuit carries blood to the entire body.  Arteries take oxygenated blood from the heart to the organs;  veins take deoxygenated blood from the organs to the heart.  The aorta is the major artery, and the venae cavae are the major veins.  Using the diagram, locate the following arteries and veins.



    Thoracic Cavity


    The coronary arteries and the cardiac veins can be seen on the surface of the heart. The carotid arteries and the jugular veins serve the neck and head regions ofthe body.  Locate these vessels.


    The subclavian arteries and veins transport blood to and from the forelimbs.  Locate these vessels.



    Abdominal Cavity


    Examine the aorta.  It may be necessary to life the left lung to observe the aorta.  The aorta may appear white in color due to its thick wall. Trace the aorta as it passes through the diaphragm and into the abdominal cavity.


    Lift the liverand the stomach and move it to the side. 


      Observe the renal arteries as they branch from the aorta.  Trace them to the kidneys.


      Locate the renal veins that leave the kidneys.  Trace the path of the renal veins to the vena cava.


      Locate the vena cava;  it is a large blue vessel dorsal to the aorta.  Trace the path of the vena cava back to the heart.



    Comparison of Blood Vessels


    Blood pressure from the pumping heart keeps blood moving in the arteries away from the heart.  The thick walls of the arteries expand when blood is pumped into them.  The contraction of skeletal muscle causes the blood to flow back tothe heart.


      Do you expect that arteries or veins will be more superficial?  Why?






      Which type of blood vessel has thicker walls?  Why?





    Observation of the Fetal Pig Heart



    Remove the heart from the pig by cutting the vessels that attach it.  Section the heart, separating the ventral from the dorsal side.  Identify the four chambers of the heart.



      With a blunt probe find the oval opening between the two-atrial chambers.  This is the shunt that allows the blood to bypass lung circulation prior to birth. 


      Would you expect to find this shunt in an adult pig?




    The Urogenital System of the Fetal Pig



    The urinary and reproductive systems are very closely associated in mammals.  The organs of each system are particulary associated in males.



      What structure is part of both the male reproductive system and the male urinary system?


      What are the major organs of the urinary system?


    The kidneys are located on the dorsal body wall wher they are held in place by connective tissue.  The renal artery and vein supply blood to the kidneys. 


      What is the function of the ureters?


      What isthe function of the urinary bladder?


      What is the function of the urethra?



    In males, sperm are produced in the seminiferous tubules of the testes.  The sperm arestored in the epididymis and carried through the vas deferens to theurethra.  The seminal vesicles, the prostate gland and the bulbourethralgland (Cowper's gland) add fluid to the semen after sperm reach theurethra. 


    In females, the eggs are produced in follicles of the ovaries.  The egg moves from the ovarytot he oviduct where fertilization occurs.  The fetus develops in theuterus.  The cervix, the opening to the uterus, connects to thevagina.  The vagina serves both as the organ of copulation and as the birth canal.



    Observation of the Urinary System of the Fetal Pig



    Urinary Comparision



    Using the diagrams observe and compare the urinary system in both sexes of fetal pigs. 

    Locate thekidney's.  These are large, paired, reddish-brown organs.  The kidneys will be found against the muscles of in the back of the pig, held inplace by the peritoneal membrane. 



      Remove one of the kidneys and cut itin half lengthwise. 

    Using the diagram, find the following structures:  renal cortex, renal medulla, and the renal pelvis.



    Kidney Cut


      What is the function of the renal pelvis?  Where is it located in the kidney?



      Where isthe renal cortex located?  The renal Medula?



    Inside the kidney, you can also find the renal pyramid. 


      What structures can befound in the renal pyramid?



      What do these structures do?



    Locate the ureters.  These are the tubes that leave the kidneys. 

      Remove the peritoneal membrane so thatyou can follow the path of the ureter down to the urinary bladder.  Locate the urinary bladder.  It may be on the flap of tissue which the umbilicalcord was attached.


    Locate the urethra;  it leaves the bladder and disappears in the pelvic girdle.


      What is the path ofurine from the kidney to the exterior of the body?




    The Male Reproductive System



    In the male the testes begin their development in the abdominal caivty, anterior and dorsal to thekidneys.  Before birth the testes descend into paired scrotal sacs withinthe scrotum.  Each scrotal sac is connected to the body cavity of the fetal pig by an inguinal canal.  You should be able to find this openingin your pig.  The movement of the testes into the scrotal sacs is reffed to as "descending".  Testes descend in both pigs and humans.  The testes in your fetal pig will be partially or fully descended.  Using this link, locate the following structures in your pig:

    Epididymis, vas deferens, penis, inguinal canal, testes, urethra.  You may be able to locatethe bulbourethral glands, the proste gland and the small, paired seminalvesicles.


      What isthe function of each of the above structures?


      Trace the path of sperm in the male from the testes to the exterior of the body.





    The Reproductive System of Female Fetal Pig


    The femalereproductive system consists of the ovaries, the oviducts and the uterus. Eggs are produced in the ovaries and are transported to the uterus by theoviducts (also called the Fallopian Tubes).  Fetal development occursin the uterus.  In the fetal pig the uterus is not a single organ asin humans.  Rather it is partially divided into two extened structurescalled uterine horns which connect with the oviduct.  The vagina is thebirth canal and the organ of sexual intercourse.

    Using this link, locate the following structures in your pig:  ovaries, oviducts, utnerine horn, vagina. The ovaries are small strucutres suspended from the peritoneal wall posteriorto the kidneys.  Locate the oviduct;  it is a small, coiledtube.  The oviduct does not attach to the ovary;  it terminates in afunnel-shaped structure that partially encloses the ovary.  Observe the uterinehorns; do not confuse the uterine horns with the oviducts.  The oviductsare very small and are very close to the ovaries.

      To observe the vagina, seperate thehind limbs of the pig and cut down the midventral line.  This cut will go through the muscle and the cartilaginous pelvic girdle.  Spread the cut edges apart and seperate the connective tissue.  There are three ductsthat pass from the body cavity to the exterior of the pig.  These includethe urethra (from the bladder), which is part of the urinarysystem.  The rectum is the end of the digestive system; it exits the bodyat the anus.  The vagina is the middle duct; it connects anteriorly to the uterus.



      What are the functions of the ovaries, oviduct, uterine horn and vagina?



      Trace thepath of an egg from the ovary to the uterus.



    Part II Review Questions




    The skeletal system of the fetal pig is similar to the human skeleton because both are mammals.  However, their are differences in the the types of bones and the shapes of bones because the of the different appearances of both organisms.

    This body system does not involve any dissection.

      What are the four major organs of the skeletal system?



      What type of connective tissue isthe fetal pig skeleton made of?



     When the pig is born what type of connective tissue will the skeleton be made of?



    Because of the lack of bones in the fetal pig, it will be neccessary to recall the dissection of the chicken leg tolook at some of the features of bones.

    Click here to see pictures of the features of the bones. 
    Compare the skeleton of the pig withthe skelton of the human. 

      What bones do you have in common with the pig?  List them and explain any structural differences.



    Fetal pigs have a muscular system that shares some common features with the human muscular system.  We will not dissect the fetal pigs muscluar system as the muscles of the fetal pig are very thin and soft.  They tear easily.  You must recall the chicken leg dissection to remember what muscles look like and how they work.


    Click here to see pictures from the chicken leg dissection of the muscles.

    What are the three types of muscle tissue?


      For each muscle type state whether it is voluntary or involuntary, striated or smoothand where it is located.




      Muscles are made of two types of protein filaments.  What are they called? What is the difference in size between the two filaments?



      What is a sarcomere and how does it work?



      How do muscles move bones?



      How are muscles arranged so as to produce movement without ever having to push a bone?


    Using the diagram, locate the musclesthat you have in common with the fetal pig.




    Day 2 DissectionActivites


    Remove the smallintestine and large intestines by cutting where the small intestine leaves thestomach and where the large intestine becomes the rectum.  Carefully cut the membranes holding the coils in the long intestinal section; straighten the intestine.  Measure (in mm) the length of the intestinetract.

    Intestinal length=               mm


    2.  If have not already done so, you may remove the heart and look at the blood vessels and chambers.


    3.  If youhave not already done so, you can remove the kidney and cut it with a front cut so that you can observe the inner structures.


    4.  You can now look at the pig's brain if you would like. This is optional. OPTIONAL.

    You need to stick the scissors into the eye socket and use that as leverage to slowly and gently chip the brain case.  The brain is very very delicate.